The present invention relates to a cylinder apparatus and a method of manufacturing a cylinder apparatus.
Japanese Utility Model Registration Application Publication No. Sho 63-26409 discloses a cylinder apparatus in which a spring seat is secured to a joint between a piston rod and a mounting eye, and one end of a dust boot is supported by the spring seat.
In Japanese Utility Model Registration Application Publication No. Sho 63-26409, the end of the piston rod is covered by the metallic spring seat. However, the portion of the piston rod projecting out of the cylinder, except the end thereof, and the end of the cylinder are covered only by the dust boot made of a plastic material. Therefore, if a pebble or the like hits the dust boot during running of the vehicle, the dust boot may be broken. In such an event, the piston rod or the end of the cylinder may be damaged.
Japanese Patent Application Publication No. 2008-45738 discloses a shock absorber (cylinder apparatus) to solve the above-described problem. The shock absorber has a first cylinder, a second cylinder provided around the outer periphery of the first cylinder with a space between itself and the first cylinder, and a third cylinder provided around the outer periphery of the second cylinder axially movably relative to the second cylinder. The third cylinder is retained at one end thereof by a bottom cover member. The bottom cover member is secured to the joint between the piston rod and the mounting eye. The overall length of the shock absorber is set not less than that of the second cylinder.
In the shock absorber (cylinder apparatus) disclosed in Japanese Patent Application Publication No. 2008-45738, however, there is no gap between the second and third cylinders, and the overall length of the third cylinder is set not less than that of the second cylinder. During assembly process, once the third cylinder has been assembled to the second cylinder, the end (mounting eye-side end) of the second cylinder cannot be staked or caulked after the bottom cover member has been assembled to the ends (mounting eye-side ends) of the first and second cylinders, for example. Therefore, the assembly of the third cylinder to the second cylinder has to be done last. Accordingly, the degree of freedom in assembly process is low, and it is difficult to streamline the manufacturing process. Another problem is that the employment of the third cylinder causes an increase in weight of the shock absorber.